I. Field of the Invention
The present invention relates to a method and a device which in the case of an internal combustion engine, allow the temperature of the exhaust gases entering a post-treatment system positioned downstream of a system for the treatment of said exhaust gases to be modeled (for example, and nonlimitingly said treatment system may be an oxidation catalyst, a nitrogen oxides NOx trap, or a “4-way” catalyst), thus making it possible to dispense with a sensor while at the same time having access to information that is essential for the correct operation of said post-treatment system.
II. Description of Related Art
Various methods for estimating the temperature within a system for treating the gases resulting from internal combustion in an engine (for example within a nitrogen oxides No trap) and installed in the exhaust system of said engine are known, since this parameter does in fact play an important part both in the efficiency of said treatment system and in its aging in particular. These methods are generally based on measuring the temperature of the exhaust gases near said treatment system (upstream or downstream thereof or, in certain cases, measuring twice, upstream and downstream/combined with a calculation based on various types of models.
Document U.S. Pat. No. 5,419,122, for example, thus proposes a method for determining the condition of a catalytic trap, in which method the temperature of the exhaust gases upstream of said trap is measured, combined with the measuring of the temperature of said gases downstream of said trap, to allow the amount of heat transferred between said exhaust gases and the catalyst in said trap to be calculated, the temperature of said catalyst then being deduced from said amount of heat using a conventional model for the transfer of heat by convection within said catalyst.
Such methods do not, however, fully take account of phenomena that arise in transient engine conditions and only partially account for the physico-chemical phenomena that occur within the catalytic trap or even ignore these completely. Now, the exothermal nature of the reactions that take place within said trap together with the thermal inertia of said trap have a not insignificant influence on the thermal condition of said trap and on its temperature: failure to take these factors into consideration may result in a somewhat unreliable estimate of the parameter being studied in models in which, furthermore, the only input data item is a temperature measurement taken outside said trap (which is therefore not particularly representative of the thermal condition within said trap).
Document DE 19836955 sets out a method for calculating the temperature within catalytic traps, in which two treatment systems are placed in series in the exhaust system of an internal combustion engine, and in which said temperature is deduced, by a method of integration, from an energy balance within each of said treatment systems, partially taking into consideration a certain amount of exothermal behavior during operation together with the thermal inertia of said systems.
This method does, however entail the fitting of several temperature sensors to the exhaust system and therefore Droves to be relatively expensive since said sensors have also to be equipped with appropriate connection equipment, thus further increasing the cost. The measurement precision of said sensors may, also, degrade as they experience thermal aging and/or become soiled, and the large number of them used here may lead to significant drifts in the reliability of the results.